CHEYENNE, Wyo. - After record mountain snowmelt caused disastrous flooding across Wyoming last year, early predictions Tuesday by federal hydrologists foresee below average runoff this year because of a dearth of snowfall so far this winter.
Based on current snowfall in the mountains, hydrologists estimate that Wyoming's runoff this year will be about 81 percent of average.
The estimate was released by the U.S. Agriculture Department's Natural Resources Conservation Service, which will issue additional estimates later this winter and into June.
"But it's still early; we can still make her back up yet," Lee Hackleman, NRCS water supply specialist, said.
Wyoming's heaviest and wettest snowfalls generally occur in April and May.
The statewide snowpack so far this winter was 80 percent of average. "The early forecasts were for it to be kind of a wet year, but it isn't panning out that way," Hackleman said. "You would think that we were still in a drought the way this year started out."
At the same time last year, the snowpack was 114 percent of average and grew into May. When the 2011 snowpack finally melted, rivers and streams were flooded and sections of mountainsides caved, causing millions of dollars in damage to cropland, roads and other infrastructure. Much of the state was declared a major federal disaster.
Most snow this winter has fallen in northern Wyoming, and NRCS runoff predictions reflect that.
The agency predicts that the Snake River Basin in northwest Wyoming will yield about 80 percent of average snowmelt and the Upper Yellowstone and Madison river basins about 93 percent of average. The Bighorn River Basin is expected to be about 95 percent of average.
Yields from the Shoshone and Clarks Fork river basins in northern Wyoming are expected to be about average, while the Tongue and Powder river basins are expected to be above average. In central and southern Wyoming, runoff is looking to be well below average with the Upper North Platte estimated at 61 percent of average, the Lower North Platte at 58 percent of average and the Wind River at 75 percent.
Estimated runoff for other basins are: Belle Fourche, 98 percent of average; Cheyenne, 91 percent; Little Snake, 76 percent; Green River, 64 percent; Little Bear, 68 percent.
Hackleman said the good news is that reservoirs in the southern part of the state are full from last year's runoff. Farmers rely on the reservoirs for irrigation water.
Statewide, reservoirs are 92 percent full.